build: Fix file format in CHANGES-staging.

One of the change files doesn't conform to the format that the release
scripts need in order to parse it.

Change-Id: Ie0b634cf27e4cbc671b9fe92993b6f2ecf60254c

doc/CHANGES-staging/res_pjsip_add_norefersub_global_config.txt

-res_pjsip:  Added a norefersub configuration setting
+Subject: res_pjsip
 
 Added a new PJSIP global setting called norefersub.
 Default is true to keep support working as before.
 
-res_pjsip_refer:  Configures PJSIP norefersub capability accordingly.
+res_pjsip_refer configures PJSIP norefersub capability accordingly.
 
 Checks the PJSIP global setting value.
 If it is true (default) it adds the norefersub capability to PJSIP.